Certain N-confused porphyrins have been known since 1994 (E. D. Steinberg et al, Tetrahedron 1998, 54, 4151-4202, see 4192 and 4193 specifically). They are of a structure that may be represented, when substituted with phenyl rings at the meso positions as herein proposed, as shown in Figure I.

Recently, Lindsey et al have published a ready synthesis of such N-confused porphyrins (G. R. Geier, D. M. Haynes, J. S. Lindsey, Organic Letters 1999, 1(9), 1455-1458).
Also known, in our European Patent Specifications Nos. 0186962 and 0337601 are tetrahydroxyphenyl derivatives of porphyrins, chlorins and bacteriochlorins, for photodynamic therapy (PDT) of cancerous tissue. These compounds have good properties and, among them, tetra(3-hydroxyphenyl)dihydroporphyrin or m-THPC is well into the stages of product development for PDT. Nevertheless, improvements in PDT compounds in respect of absorption wavelength and hence depths of PDT necrosis, tissue selectivity, water-compatibility, and ease of synthesis are sought. PDT compounds also have application as light activated agents with the power to kill viruses and bacteria that are now proving resistant to conventional antibiotics.